# Directional Sensitivity In Light-Mass Dark Matter Searches With Single-Electron Resolution Ionization Detectors [CL]

We present a method for using solid state detectors with directional sensitivity to dark matter interactions to detect low-mass Weakly Interacting Massive Particles (WIMPs) originating from galactic sources. In spite of a large body of literature for high-mass WIMP detectors with directional sensitivity, there is no available technique to cover WIMPs in the mass range <1 GeV. We argue that single-electron resolution semiconductor detectors allow for directional sensitivity once properly calibrated. We examine commonly used semiconductor material response to these low-mass WIMP interactions.

F. Kadribasic, N. Mirabolfathi, K. Nordlund, et. al.
Fri, 17 Mar 17
32/50

# Aqua MODIS Band 24 Crosstalk Striping [IMA]

Aqua MODIS, unlike its predecessor on board the Terra spacecraft, had always been thought to have been spared from significant deleterious impacts of electronic crosstalk on its imagery. However, recent efforts brought to our attention the presence of striping artifacts in Aqua MODIS images from band 24 (4.47$\mu$m), which upon further inspection proved to have a noticeable impact on the quality of the L1B product and to have been present since the beginning of the mission, in 2002. Using images of the Moon from scheduled lunar observations, we linked the artifacts with electronic crosstalk contamination of the response of detector 1 of band 24 by signal sent from the detector 10 of band 26 (1.375$\mu$m), a neighboring band in the same focal plane assembly. In this paper, we report on these findings, the artifact mitigation strategy adopted by us, and on our success in restoring band 24 detector 1 behavior and image quality.

G. Keller, Z. Wang, A. Wu, et. al.
Thu, 16 Mar 17
24/92

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# The Novel ABALONE Photosensor Technology [CL]

The patented and proven ABALONE Photosensor Technology (Daniel Ferenc, U.S. Patent 9,064,678, 2010) has the capability of opening new horizons in the fields of fundamental physics, functional medical imaging, and nuclear security. This article discusses our new technology and overviews the unprecedented performance of ABALONE Photosensors, produced in the custom designed production line at UC Davis and continuously tested since 2013. In conclusion, the modern ABALONE Technology is far superior to prior art in performance, robustness and the capacity for integration into large area detector shells. It is about two orders of magnitude more cost effective while being mass-producible with a relatively low investment.

D. Ferenc, A. Chang and M. Ferenc
Thu, 16 Mar 17
44/92

Comments: 16 pages, 7 figures, Submitted for publication to Nuclear Instruments And Methods In Physics Research A on March 12, 2017 (Ms. Ref. No.: NIMA-D-17-00243)

# Gain factor and parameter settings optimization of the new gamma-ray burst polarimeter POLAR [IMA]

As a space-borne detector POLAR is designed to conduct hard X-ray polarization measurements of gamma-ray bursts on the statistically significant sample of events and with an unprecedented accuracy. During its development phase a number of tests, calibrations runs and verification measurements were carried out in order to validate instrument functionality and optimize operational parameters. In this article we present results on gain optimization togeter with verification data obtained in the course of broad laboratory and environmental tests. In particular we focus on exposures to the $^{137}$Cs radioactive source and determination of the gain dependence on the high voltage for all 1600 detection channels of the polarimeter. Performance of the instrument is described in detail with respect to the dynamic range, energy resolution and temperature dependence. Gain optimization algorithms and response non-uniformity studies are also broadly discussed. Results presented below constitute important parts for development of the POLAR calibration and operation database.

X. Zhang, W. Hajdas, H. Xiao, et. al.
Tue, 14 Mar 17
17/74

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# Sensitivity Characterization of a Parametric Transducer for Gravitational Wave Detection Through Optomechanical Spring Effect [IMA]

We present the characterization of the most recent parametric transducers designed to enhance the Mario Schenberg Gravitational Wave Detector sensitivity. The transducer is composed of a microwave re-entrant cavity that attaches to the gravitational wave antenna via a rigid spring. It functions as a three-mode mass-spring system; motion of the spherical antenna couples to a 50 $\mu$m thick membrane, which converts its mechanical motion into a frequency shift of the cavity resonance. Through the optomechanical spring effect, the microwave transducer frequency-displacement sensitivity was measured to be 726 MHz/$\mu$m at 4 K. The spherical antenna detection sensitivity is determined analytically using the transducer amplification gain and equivalent displacement noise in the test setup to be $5.5 \times 10^{-19}\sqrt{Hz}^{-1}$.

N. Carvalho, J. Bourhill, O. Aguiar, et. al.
Wed, 8 Mar 17
26/60

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# Search for axions in streaming dark matter [CL]

A new search strategy for the detection of the elusive dark matter (DM) axion is proposed. The idea is based on streaming DM axions, whose flux might get temporally enormously enhanced due to gravitational lensing. This can happen if the Sun or some planet (including the Moon) is found along the direction of a DM stream propagating towards the Earth location. The experimental requirements to the axion haloscope are a wide-band performance combined with a fast axion rest mass scanning mode, which are feasible. Once both conditions have been implemented in a haloscope, the axion search can continue parasitically almost as before. Interestingly, some new DM axion detectors are operating wide-band by default. In order not to miss the actually unpredictable timing of a potential short duration signal, a network of co-ordinated axion antennae is required, preferentially distributed world-wide. The reasoning presented here for the axions applies to some degree also to any other DM candidates like the WIMPs.

K. Zioutas, V. Anastassopoulos, S. Bertolucci, et. al.
Tue, 7 Mar 17
65/66

# Understanding NaI(Tl) crystal background for dark matter searches [IMA]

We have developed ultra-low-background NaI(Tl) crystals to reproduce the DAMA results with the ultimate goal of achieving purity levels that are comparable to or better than those of the DAMA/LIBRA crystals. Even though the achieved background level does not approach that of DAMA/LIBRA, it is crucial to have a quantitative understanding of the backgrounds. We describe the contributions of background sources quantitatively by performing Geant4 Monte Carlo simulations that are fitted to the measured data to quantify the unknown fractions of the background compositions. The overall simulated background spectrum well describes the measured data with a 9.16-kg NaI(Tl) crystal and shows that the background sources are dominated by surface $^{210}$Pb and internal $^{40}$K in the 2 to 6-keV energy interval, which produce 2.31 counts/day/keV/kg (dru) and 0.48 dru, respectively.

Tue, 7 Mar 17
66/66

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# Light yield determination in large sodium iodide detectors applied in the search for dark matter [CL]

Application of NaI(Tl) detectors in the search for galactic dark matter particles through their elastic scattering off the target nuclei is well motivated because of the long standing DAMA/LIBRA highly significant positive result on annual modulation, still requiring confirmation. For such a goal, it is mandatory to reach very low threshold in energy (at or below the keV level), very low radioactive background (at a few counts/keV/kg/day), and high detection mass (at or above the 100 kg scale). One of the most relevant technical issues is the optimization of the crystal intrinsic scintillation light yield and the efficiency of the light collecting system for large mass crystals. In the frame of the ANAIS (Annual modulation with NaI Scintillators) dark matter search project large NaI(Tl) crystals from different providers coupled to two photomultiplier tubes (PMTs) have been tested at the Canfranc Underground Laboratory. In this paper we present the estimates of the NaI(Tl) scintillation light collected using full-absorption peaks at very low energy from external and internal sources emitting gammas/electrons, and single-photoelectron events populations selected by using very low energy pulses tails. Outstanding scintillation light collection at the level of 15~photoelectrons/keV can be reported for the final design and provider chosen for ANAIS detectors. Taking into account the Quantum Efficiency of the PMT units used, the intrinsic scintillation light yield in these NaI(Tl) crystals is above 40~photoelectrons/keV for energy depositions in the range from 3 up to 25~keV. This very high light output of ANAIS crystals allows triggering below 1~keV, which is very important in order to increase the sensitivity in the direct detection of dark matter.

M. Olivan, J. Amare, S. Cebrian, et. al.
Mon, 6 Mar 17
35/47

# The Plastic Scintillator Detector at DAMPE [IMA]

he DArk Matter Particle Explorer (DAMPE) is a general purposed satellite-borne high energy $\gamma-$ray and cosmic ray detector, and among the scientific objectives of DAMPE are the searches for the origin of cosmic rays and an understanding of Dark Matter particles. As one of the four detectors in DAMPE, the Plastic Scintillator Detector (PSD) plays an important role in the particle charge measurement and the photons/electrons separation. The PSD has 82 modules, each consists of a long organic plastic scintillator bar and two PMTs at both ends for readout, in two layers and covers an overall active area larger than 82 cm $\times$ 82 cm. It can identify the charge states for relativistic ions from H to Fe, and the detector efficiency for Z=1 particles can reach 0.9999. The PSD has been successfully launched with DAMPE on Dec. 17, 2015. In this paper, the design, the assembly, the qualification tests of the PSD and some of the performance measured on the ground have been described in detail.

Y. Yu, Z. Sun, H. Su, et. al.
Thu, 2 Mar 17
25/44

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# Frequency stability characterization of a broadband fiber Fabry-Perot interferometer [IMA]

An optical etalon illuminated by a white light source provides a broadband comb-like spectrum that can be employed as a calibration source for astronomical spectrographs in radial velocity (RV) surveys for extrasolar planets. For this application the frequency stability of the etalon is critical, as its transmission spectrum is susceptible to frequency fluctuations due to changes in cavity temperature, optical power and input polarization. In this paper we present a laser frequency comb measurement technique to characterize the frequency stability of a custom-designed fiber Fabry-Perot interferometer (FFP). Simultaneously probing the stability of two etalon resonance modes, we assess both the absolute stability of the etalon and the long-term stability of the cavity dispersion. We measure mode positions with MHz precision, which corresponds to splitting the FFP resonances by a part in 500 and to RV precision of ~1 m/s. We address limiting systematic effects, including the presence of parasitic etalons, that need to be overcome to push the metrology of this system to the equivalent RV precision of 10 cm/s. Our results demonstrate a means to characterize environmentally-driven perturbations of etalon resonance modes across broad spectral bandwidths, as well as motivate the benefits and challenges of FFPs as spectrograph calibrators.

J. Jennings, S. Halverson, R. Terrien, et. al.
Thu, 2 Mar 17
41/44

Comments: 13 pages, 7 figures, submitted to Opt. Express

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# First Demonstration of a Scintillating Xenon Bubble Chamber for Dark Matter and CE$ν$NS Detection [CL]

A 30-gram xenon bubble chamber, operated at Northwestern University in June and November 2016, has for the first time observed simultaneous bubble nucleation and scintillation by nuclear recoils in liquid xenon. This chamber is instrumented with a CCD camera for near-IR bubble imaging, a solar-blind PMT to detect 175-nm xenon scintillation light, and a piezoelectric acoustic transducer to detect the ultrasonic emission from a growing bubble. The time-of-nucleation determined from the acoustic signal is used to correlate specific scintillation pulses with bubble-nucleating events. The observed single- and multiple-bubble rates when exposed to a $^{252}$Cf neutron source indicate that, for a thermodynamic “Seitz” threshold of 8.3 keV, the minimum nuclear recoil energy required to nucleate a bubble is between 11 and 25 keV. This is consistent with the observed scintillation spectrum for bubble-nucleating events. We see no evidence for bubble nucleation by gamma rays at the thresholds studied, setting a 90% CL upper limit of $6.3\times10^{-7}$ bubbles per gamma interaction at a 4.2-keV thermodynamic threshold. This indicates stronger gamma discrimination than in CF$_3$I bubble chambers, supporting the hypothesis that scintillation production suppresses bubble nucleation by electron recoils, while nuclear recoils nucleate bubbles as usual. These measurements establish the noble-liquid bubble chamber as a promising new technology for WIMP and CE$\nu$NS detection.

D. Baxter, C. Chen, M. Crisler, et. al.
Wed, 1 Mar 17
40/67

# Short-baseline electron antineutrino disappearance study by using neutrino sources from $^{13}$C + $^{9}$Be reaction [CL]

To investigate the existence of sterile neutrino, we propose a new neutrino production method using $^{13}$C beams and a $^{9}$Be target for short-baseline electron antineutrino (${\bar{\nu}}_{e}$) disappearance study. The production of secondary unstable isotopes which can emit neutrinos from the $^{13}$C + $^{9}$Be reaction is calculated with three different nucleus-nucleus (AA) reaction models. Different isotope yields are obtained using these models, but the results of the neutrino flux are found to have unanimous similarities. This feature gives an opportunity to study neutrino oscillation through shape analysis. In this work, expected neutrino flux and event rates are discussed in detail through intensive simulation of the light ion collision reaction and the neutrino flux from the beta decay of unstable isotopes followed by this collision. Together with the reactor and accelerator anomalies, the present proposed ${\bar{\nu}}_{e}$ source is shown to be a practically alternative test of the existence of the $\Delta m^{2}$ $\sim$ 1 eV$^{2}$ scale sterile neutrino.

J. Shin, M. Cheoun, T. Kajino, et. al.
Tue, 28 Feb 17
50/69

# HARPO: 1.7 – 74 MeV gamma-ray beam validation of a high angular resolutio n, high linear polarisation dilution, gas time projection chamber telescope and polarimeter [IMA]

A presentation at the SciNeGHE conference of the past achievements, of the present activities and of the perspectives for the future of the HARPO project, the development of a time projection chamber as a high-performance gamma-ray telescope and linear polarimeter in the e+e- pair creation regime.

D. Bernard
Tue, 28 Feb 17
65/69

Comments: Presented at SciNeGHE 2016 “11th Workshop on Science with the New generation of High Energy Gamma-ray Experiments : High-energy gamma-ray experiments at the dawn of gravitational wave astronomy” 18-21 October 2016, Pisa, Italy. Proceedings to be submitted to Il Nuovo Cimento

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# Dark Matter Search Results from the PICO-60 C$_3$F$_8$ Bubble Chamber [CEA]

New results are reported from the operation of the PICO-60 dark matter detector, a bubble chamber filled with 52 kg of C$_3$F$_8$ located in the SNOLAB underground laboratory. As in previous PICO bubble chambers, PICO-60 C$_3$F$_8$ exhibits excellent electron recoil and alpha decay rejection, and the observed multiple-scattering neutron rate indicates a single-scatter neutron background of less than 1 event per month. A blind analysis of an efficiency-corrected 1167-kg-day exposure at a 3.3-keV thermodynamic threshold reveals no single-scattering nuclear recoil candidates, consistent with the predicted background. These results set the most stringent direct-detection constraint to date on the WIMP-proton spin-dependent cross section at 3.4 $\times$ 10$^{-41}$ cm$^2$ for a 30-GeV$\thinspace$c$^{-2}$ WIMP, more than one order of magnitude improvement from previous PICO results.

C. Amole, M. Ardid, I. Arnquist, et. al.
Mon, 27 Feb 17
39/49

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# Performance of a continuously rotating half-wave plate on the POLARBEAR telescope [IMA]

A continuously rotating half-wave plate (CRHWP) is a promising tool to improve the sensitivity to large angular scales in cosmic microwave background (CMB) polarization measurements. With a CRHWP, single detectors can measure all three of the Stokes parameters, $I$, $Q$ and $U$, thereby avoiding the set of systematic errors that can be introduced by mismatches in the properties of orthogonal detector pairs. We focus on the implementation of CRHWPs in large aperture telescopes (i.e. the primary mirror is larger than the current maximum half-wave plate diameter of $\sim$0.5 m), where the CRHWP can be placed between the primary mirror and focal plane. In this configuration, one needs to address the intensity to polarization ($I{\rightarrow}P$) leakage of the optics, which becomes a source of 1/f noise and also causes differential gain systematics that arise from CMB temperature fluctuations. In this paper, we present the performance of a CRHWP installed in the POLARBEAR experiment, which employs a Gregorian telescope with a 2.5 m primary illumination pattern. The CRHWP is placed near the prime focus between the primary and secondary mirrors. We find that the $I{\rightarrow}P$ leakage is larger than the expectation from the physical properties of our primary mirror, resulting in a 1/f knee of 100 mHz. The excess leakage could be due to imperfections in the detector system, i.e. detector non-linearity in the responsivity and time-constant. We demonstrate, however, that by subtracting the leakage correlated with the intensity signal, the 1/f noise knee frequency is reduced to 32 mHz ($\ell \sim$39 for our scan strategy), which is sufficient to probe the primordial B-mode signal. We also discuss methods for further noise subtraction in future projects where the precise temperature control of instrumental components and the leakage reduction will play a key role.

S. Takakura, M. Aguilar, Y. Akiba, et. al.
Fri, 24 Feb 17
4/50

Comments: 27 pages, 5 figures, 3 tables, to be submitted to JCAP

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# Cosmic Ray RF detection with the ASTRONEU array [CL]

Results will be shown from the ASTRONEU array developed and operated in the outskirts of Patras, Greece. An array of 9 scintillator detectors and 3 antennas were deployed to study Extensive Air Showers (EAS) as a tool for calibrating an underwater neutrino telescope, possible other applications in muon tomography, education purposes, and last but not least, the detection of air showers via their electromagnetic signature. This is the first stage of a total of 24 scintillator counters and 6 RF antennas to complete the array. In this work, results with regard to the electromagnetic detection of showers will be shown. The method of operation and analysis will be presented. The purpose of this project was to demonstrate the adequacy of the method to detect cosmic events even in the presence of high urban electromagnetic background, using noise filters, timing, signal polarization, and eventual comparison with well understood event reconstruction using the scintillator detectors. The results indicate that cosmic showers were detected and the method can be used for the complete array.

I. Manthos, I. Gkialas, G. Bourlis, et. al.
Tue, 21 Feb 17
1/70

# Electron train backgrounds in liquid xenon dark matter search detectors are indeed due to thermalization and trapping [CL]

Electron emission from liquid into gaseous xenon is a cornerstone of dark matter search detectors such as ZEPLIN, XENON, LUX and LZ. The probability of emission is a function of the applied electric field E, and electrons which fail to pass from the liquid into the gas have been previously hypothesized to become thermalized and trapped. This article shows, for the first time, quantitative agreement between an electron emission model and existing data. The model predicts that electrons in the liquid must surmount a typical potential barrier phi_b=0.34+-0.01 eV in order to escape into the gas. This value is a factor of about x2 smaller than has previously been calculated or inferred. Knowledge of phi_b allows calculation of the lifetime of thermalized, trapped electrons. The value is O(10) ms, which appears to be compatible with XENON10 observations of electron train backgrounds. As these backgrounds limit the sensitivity of dark sector dark matter searches, possible mitigations are discussed.

P. Sorensen
Fri, 17 Feb 17
26/43

# Non-Invertibility of spectral x-ray photon counting data with pileup [CL]

-In the Alvarez-Macovski method [R.E. Alvarez and A. Macovski, Phys. Med. Biol., 1976, 733-744], the attenuation coefficient is approximated as a linear combination of functions of energy multiplied by coefficients that depend on the material composition at points within the object. The method then computes the line integrals of the basis set coefficient from measurements with different x-ray spectra. This paper shows that the transformation from photon counting detector data with pileup to the line integrals can become ill-conditioned under some circumstances leading to highly increased noise. Methods: An idealized model that includes pileup and quantum noise is used. The noise variance of the line integral estimates is computed using the Cram{\`e}r-Rao lower bound (CRLB). The CRLB is computed as a function of object thickness for photon counting detector data with three and four bin pulse height analysis (PHA) and low and high pileup. Results: With four bin PHA data the transformation is well conditioned with either high or low pileup. With three bin PHA and high pileup, the transformation becomes ill-conditioned for specific values of object attenuation. At these values the CRLB variance increases by approximately 10 5 compared with the four bin PHA or low pileup results. The condition number of the forward transformation matrix also shows a spike at those attenuation values. Conclusion: Designers of systems using counting detectors should study the stability of the line integral estimator output with their data.

R. Alvarez
Fri, 17 Feb 17
42/43

# Photon emission and atomic collision processes in two-phase argon doped with xenon and nitrogen [CL]

We present a comprehensive analysis of photon emission and atomic collision processes in two-phase argon doped with xenon and nitrogen. The dopants are aimed to convert the VUV emission of pure Ar to the UV emission of the Xe dopant in the liquid phase and to the near UV emission of the N2 dopant in the gas phase. Such a mixture is relevant to two-phase dark matter and low energy neutrino detectors, with enhanced photon collection efficiency for primary and secondary scintillation signals. Based on this analysis, we show that the recently proposed hypothesis of the enhancement of the excitation transfer from Ar to N2 species in the two-phase mode is either incorrect or needs assumption about a new extreme mechanism of excitation transfer coming into force at lower temperatures, in particular that of the resonant excitation transfer via ArN2 compound (van der Waals molecule).

A. Buzulutskov
Tue, 14 Feb 17
19/71

Comments: 6 pages, 1 figure, 1 table

# Quantum correlation measurements in interferometric gravitational wave detectors [CL]

Quantum fluctuations in the phase and amplitude quadratures of light set limitations on the sensitivity of modern optical instruments. The sensitivity of the interferometric gravitational wave detectors, such as the Advanced Laser Interferometer Gravitational wave Observatory (LIGO), is limited by quantum shot noise, quantum radiation pressure noise, and a set of classical noises. We show how the quantum properties of light can be used to distinguish these noises using correlation techniques. Particularly, in the first part of the paper we show estimations of the coating thermal noise and gas phase noise, hidden below the quantum shot noise in the Advanced LIGO sensitivity curve. We also make projections on the observatory sensitivity during the next science runs. In the second part of the paper we discuss the correlation technique that reveals the quantum radiation pressure noise from the background of classical noises and shot noise. We apply this technique to the Advanced LIGO data, collected during the first science run, and experimentally estimate the quantum correlations and quantum radiation pressure noise in the interferometer for the first time.

D. Martynov, V. Frolov, S. Kandhasamy, et. al.
Tue, 14 Feb 17
29/71

# First On-Site True Gamma-Ray Imaging-Spectroscopy of Contamination near Fukushima Plant [CL]

We have developed an Electron Tracking Compton Camera (ETCC), which provides a well-defined Point Spread Function (PSF) by reconstructing a direction of each gamma as a point and realizes simultaneous measurement of brightness and spectrum of MeV gamma-rays for the first time. Here, we present the results of our on-site pilot gamma-imaging-spectroscopy with ETCC at three contaminated locations in the vicinity of the Fukushima Daiichi Nuclear Power Plants in Japan in 2014. The obtained distribution of brightness (or emissivity) with remote-sensing observations is unambiguously converted into the dose distribution. We confirm that the dose distribution is consistent with the one taken by conventional mapping measurements with a dosimeter physically placed at each grid point. Furthermore, its imaging spectroscopy, boosted by Compton-edge-free spectra, reveals complex radioactive features in a quantitative manner around each individual target point in the background-dominated environment. Notably, we successfully identify a “micro hot spot” of residual caesium contamination even in an already decontaminated area. These results show that the ETCC performs exactly as the geometrical optics predicts, demonstrates its versatility in the field radiation measurement, and reveals potentials for application in many fields, including the nuclear industry, medical field, and astronomy.

D. Tomono, T. Mizumoto, A. Takada, et. al.
Fri, 10 Feb 17
6/46

Comments: 19 pages, 7 figures, 2 tables

# Establishment of Imaging Spectroscopy of Nuclear Gamma-Rays based on Geometrical Optics [CL]

Since the discovery of nuclear gamma-rays, its imaging has been limited to pseudo imaging, such as Compton Camera (CC) and coded mask. Pseudo imaging does not keep physical information (intensity, or brightness in Optics) along a ray, and thus is capable of no more than qualitative imaging of bright objects. To attain quantitative imaging, cameras that realize geometrical optics is essential, which would be, for nuclear MeV gammas, only possible via complete reconstruction of the Compton process. Recently we have revealed that “Electron Tracking Compton Camera” (ETCC) provides a well-defined Point Spread Function (PSF). The information of an incoming gamma is kept along a ray with the PSF and that is equivalent to geometrical optics. Here we present an imaging-spectroscopic measurement with the ETCC. Our results highlight the intrinsic difficulty with CCs in performing accurate imaging, and show that the ETCC surmounts this problem. The imaging capability also helps the ETCC suppress the noise level dramatically by ~3 orders of magnitude without a shielding structure. Furthermore, full reconstruction of Compton process with the ETCC provides spectra free of Compton edges. These results mark the first proper imaging of nuclear gammas based on the genuine geometrical optics.

T. Tanimori, Y. Mizumura, A. Takada, et. al.
Fri, 10 Feb 17
40/46

# Radiogenic Neutron Yield Calculations for Low-Background Experiments [CL]

Nuclear recoil backgrounds are one of the most dangerous backgrounds for many dark matter experiments. A primary source of nuclear recoils is radiogenic neutrons produced in the detector material itself. These neutrons result from fission and $(\alpha,n)$ reactions originating from uranium and thorium contamination. In this paper, we discuss neutron yields from these sources. We compile a list of $(\alpha,n)$ yields for many materials common in low-background detectors, calculated using NeuCBOT, a new tool introduced in this paper, available at https://github.com/shawest/neucbot. These calculations are compared to computations made using data compilations and SOURCES-4A

S. Westerdale and P. Meyers
Thu, 9 Feb 17
64/67

# Mitigating radiation damage of single photon detectors for space applications [CL]

Single-photon detectors in space must retain useful performance characteristics despite being bombarded with sub-atomic particles. Mitigating the effects of this space radiation is vital to enabling new space applications which require high-fidelity single-photon detection. To this end, we conducted proton radiation tests of various models of avalanche photodiodes (APDs) and one model of photomultiplier tube potentially suitable for satellite-based quantum communications. The samples were irradiated with 106 MeV protons at doses equivalent to lifetimes of 0.6 months, 6 months, 12 months and 24 months in a low-Earth polar orbit. Although most detection properties were preserved, including effciency, timing jitter and afterpulsing probability, all APD samples demonstrated significant increases in dark count rate (DCR) due to radiation-induced damage, many orders of magnitude higher than the 200 counts per second (cps) required for ground-tosatellite quantum communications. We then successfully demonstrated the mitigation of this DCR degradation through the use of deep cooling, to as low as -86 degrees C. This achieved DCR below the required 200 cps over the 24 months orbit duration. DCR was further reduced by thermal annealing at temperatures of +50 to +100 degrees C.

E. Anisimova, B. Higgins, J. Bourgoin, et. al.
Tue, 7 Feb 17
17/64

# Hellenic Open University Reconstruction & Simulation (HOURS) software package: User Guide & short reference of Event Generation, Cherenkov photon production and Optical Module simulation [IMA]

In this document the simulation part of the Hellenic Open University Reconstruction & Simulation (HOURS) software package is described in detail. HOURS can be used for the generation, simulation, pattern recognition and reconstruction of high energy neutrino produced events in a very large volume neutrino telescope. The objective is to provide as accurate as possible a representation of event properties in a wide range of neutrino telescope configurations and medium optical properties. Moreover, HOURS contains software for the simulation and reconstruction of Extensive Air Showers (EAS) using the HEllenic LYceum Cosmic Observatories Network (HELYCON) scintillation counters. Using the information offered by the simulation/reconstruction of any EAS, and by considering the showers’ energetic muons that penetrate the sea to the depth of the neutrino telescope, it is possible to study the joint performance of the neutrino and EAS detectors for physics or calibration purposes. HOURS has been used extensively for the optimization, development of calibration techniques and performance evaluation of the planned Mediterranean neutrino telescope, KM3NeT (km 3 Neutrino Telescope). The results of these studies have been published to various international scientific journals. The code and further information may be found on the HOURS web page: this http URL .

A. Tsirigotis, G. Bourlis, A. Leisos, et. al.
Mon, 6 Feb 17
6/43

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# Antonella: A nuclear-recoil ionization-efficiency measurement in silicon at low energies [CL]

We have measured the ionization efficiency of silicon nuclear recoils with kinetic energy between 1.8 and 20 keV. We bombarded a silicon-drift diode with a neutron beam to perform an elastic-scattering experiment. A broad-energy neutron spectrum was used and the nuclear recoil energy was reconstructed with the time-of-flight technique. The overall trend of the results of this work are well described by the theory of Lindhard et al. above 4 keV of recoil energy. Below this energy, the presented data shows a deviation from the model. The data indicates a faster drop than the extrapolation of the Lindhard theory to low energies.

F. Izraelevitch, D. Amidei, A. Aprahamian, et. al.
Mon, 6 Feb 17
12/43

# A 100-ps Multi-Time over Threshold Data Acquisition System for Cosmic Ray Detection [CL]

High-energy cosmic rays are one of the primary sources of information for scientists investigating the elementary properties of matter. The need to study cosmic rays, with energies thousands of times larger than those encountered in particle accelerators, led to the development of modern detection hardware and experimental methodologies. We present a low power, low complexity data acquisition (DAQ) system with 100 ps resolution, suitable for particle and radiation detection experiments. The system uses a Multiple-Time-over-Threshold (MToT) technique for the treatment of the output signal of Photo Multiplier Tubes (PMTs). The use of three thresholds compensates for the slewing effects and offers a more accurate measurement of the PMT pulses’ width. For the evaluation of the pulse the system uses comparators and a Time-to-Digital (TDC) converter, whereas the pulses are time-stamped using the GPS signal. The prototype card is analyzed for its noise behavior and is tested to verify its performance. The system has been designed for the HEllenic LYceum Cosmic Observatories Network (HELYCON) Extensive Air Showers (EAS) detector.

K. Georgakopoulou, C. Spathis, G. Bourlis, et. al.
Mon, 6 Feb 17
31/43

# Study of radiation background at various high altitude locations in preparation for rare event search in cosmic rays [CL]

Various phenomenological models presented over the years have hinted at the possible presence of strangelets, which are nuggets of Strange Quark Matter (SQM), in cosmic rays. One way to search for such rare events is through the deployment of large area Nuclear Track Detector (NTD) arrays at high mountain altitudes. Before the deployment of any such array can begin, a detailed study of the radiation background is essential. Also a proper understanding of the response of detectors exposed to extreme weather conditions is necessary. With that aim, pilot studies were carried out at various high altitude locations in India such as Darjeeling (2200 m a.m.s.l), Ooty (2200 m a.m.s.l) and Hanle (4500 m a.m.s.l). Small arrays of CR-39 as well as high threshold Polyethylene Terephthalate (PET) detectors were given open air exposures for periods ranging from three months to two years. The findings of such studies are reported in this paper.

R. Bhattacharyya, S. Dey, S. Ghosh, et. al.
Fri, 3 Feb 17
31/55

# Study of the performance of the HEPD apparatus for the CSES mission [IMA]

The High-Energy Particle Detector (HEPD) is one of the payloads of the CSES space mission. The CSES (China Seismo-Electromagnetic Satellite) mission will investigate the structure and the dynamic of the topside ionosphere, will monitor electric and magnetic field and high energy particle fluctuations, searching for their correlations with the geophysical activity, in order to contribute to the monitoring of earthquakes from space. The HEPD is built by the Italian collaboration and has different goals. It will study the temporal stability of the inner Van Allen radiation belts, the precipitation of trapped particles in the atmosphere and the low energy component of the cosmic rays (5 – 100 MeV for electrons and 15 – 300 MeV for protons). Here is presented a study of the performance of the apparatus to separate electrons and protons and identify nuclei up to iron.

B. Panico, F. Palma and A. Sotgiu
Wed, 1 Feb 17
42/67

Comments: XXV ECRS 2016 Proceedings – eConf C16-09-04.3

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# Electrothermal Feedback in Kinetic Inductance Detectors [IMA]

In Kinetic Inductance Detectors (KIDs) and other similar applications of superconducting microresonators, both the large and small-signal behaviour of the device may be affected by electrothermal feedback. Microwave power applied to read out the device is absorbed by and heats the superconductor quasiparticles, changing the superconductor conductivity and hence the readout power absorbed in a positive or negative feedback loop. In this work, we explore numerically the implications of an extensible theoretical model of a generic superconducting microresonator device for a typical KID, incorporating recent work on the power flow between superconductor quasiparticles and phonons. This model calculates the large-signal (changes in operating point) and small-signal behaviour of a device, allowing us to determine the effect of electrothermal feedback on device responsivity and noise characteristics under various operating conditions. We also investigate how thermally isolating the device from the bath, for example by designing the device on a membrane only connected to the bulk substrate by thin legs, affects device performance. We find that at a typical device operating point, positive electrothermal feedback reduces the effective thermal conductance from the superconductor quasiparticles to the bath, and so increases responsivity to signal (pair-breaking) power, increases noise from temperature fluctuations, and decreases the Noise Equivalent Power (NEP). Similarly, increasing the thermal isolation of the device while keeping the quasiparticle temperature constant decreases the NEP, but also decreases the device response bandwidth.

T. Guruswamy, C. Thomas, S. Withington, et. al.
Wed, 1 Feb 17
54/67

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# The electronics of the HEPD of the CSES experiment [IMA]

The China Seismo Electromagnetic Satellite (CSES) aims to contribute to the monitoring of earthquakes from space. This space mission, lead by a Chinese-Italian collaboration, will study phenomena of electromagnetic nature and their correlation with the geophysical activity. The satellite will be launched in 2017 and will host several instruments onboard: two magnetometers, an electrical field detector, a plasma analyzer, a Langmiur probe and the High Energy Particle Detector (HEPD). The HEPD, built by the Italian collaboration, will study the temporal stability of the inner Van Allen radiation belts, investigating precipitation of trapped particles induced by magnetospheric, ionosferic and tropospheric electromagnetic emissions, as well as by seismo-electromagnetic disturbances. It consists of two layers of plastic scintillators for trigger and a calorimeter. The direction of the incident particle is provided by two planes of double-side silicon microstrip detectors. HEPD is capable of separating electrons and protons and identify nuclei up to Iron. The HEPD will study the low energy component of cosmic rays too. The HEPD comprises the following subsystems: detector, electronics, power supply and mechanics. The electronics can be divided in three blocks: silicon detector, scintillator detectors (trigger, energy and veto detectors) and global control and data managing. In this paper a description of the electronics of the HEPD and its main characteristics will be presented.

V. Scotti, G. Osteria and Limadou. Collaboration-CSES
Fri, 27 Jan 17
45/54

Comments: XXV ECRS 2016 Proceedings – eConf C16-09-04.3

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# TRAGALDABAS. First results on cosmic ray studies and their relation with the solar activity, the Earth magnetic field and the atmospheric properties [HEAP]

Cosmic rays originating from extraterrestrial sources are permanently arriving at Earth atmosphere, where they produce up to billions of secondary particles. The analysis of the secondary particles reaching to the surface of the Earth may provide a very valuable information about the Sun activity, changes in the geomagnetic field and the atmosphere, among others. In this article, we present the first preliminary results of the analysis of the cosmic rays measured with a high resolution tracking detector, TRAGALDABAS, located at the Univ. of Santiago de Compostela, in Spain.

J. Garzon, J. Collazo, J. Cuenca-Garcia, et. al.
Thu, 26 Jan 17
25/68

Comments: XXV ECRS 2016 Proceedings – eConf TBA

# Krypton and radon background in the PandaX-I dark matter experiment [IMA]

We discuss an in-situ evaluation of the $^{85}$Kr, $^{222}$Rn, and $^{220}$Rn background in PandaX-I, a 120-kg liquid xenon dark matter direct detection experiment. Combining with a simulation, their contributions to the low energy electron-recoil background in the dark matter search region are obtained.

S. Li, X. Chen, X. Cui, et. al.
Thu, 26 Jan 17
67/68

Comments: Version as accepted by JINST

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# The second knee observed in the local muon density spectra at various zenith angles [HEAP]

Local muon density spectra (LMDS) at various zenith angles have been reconstructed from the data of two detectors of the Experimental complex NEVOD. The inclined muon bundles at the ground level were detected with the coordinate detector DECOR, and for the near-vertical direction with the calibration telescope system (CTS) of the Cherenkov water detector. In comparison with the earlier DECOR results, the experimental statistics has been increased by 2-3 times for different ranges of zenith angle and muon bundle multiplicity and is now based on about 40,000 h of the setup operation. The live time of measurements with CTS is about 12,000 h. It is found with both setups that the slope of LMDS is increasing above the primary energy of about 1017 eV. The details of the experiment and data analysis are presented.

R. Kokoulin, M. Amelchakov, N. Barbashina, et. al.
Wed, 25 Jan 17
39/74

Comments: XXV ECRS 2016 Proceedings – eConf C16-09-04.3

# High-energy neutrino astronomy with KM3NeT-ARCA [IMA]

The KM3NeT/ARCA high energy neutrino telescope is currently under construction in the Mediterranean sea. The detector will consist of two blocks of instrumented structures and will have a size of the order of a cubic-kilometer. In this work the status of the detector, the expected performance to galactic and extragalactic neutrino sources, the results from prototypes and the first deployed lines will be briefly reported.

R. Coniglione
Mon, 23 Jan 17
21/55

Comments: XXV ECRS 2016 Proceedings – eConf C16-09-04.3

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# Localisation of gamma-ray interaction points in thick monolithic CeBr3 and LaBr3:Ce scintillators [IMA]

Localisation of gamma-ray interaction points in monolithic scintillator crystals can simplify the design and improve the performance of a future Compton telescope for gamma-ray astronomy. In this paper we compare the position resolution of three monolithic scintillators: a 28x28x20 mm3 (length x breadth x thickness) LaBr3:Ce crystal, a 25x25x20 mm3 CeBr3 crystal and a 25x25x10 mm3 CeBr3 crystal. Each crystal was encapsulated and coupled to an array of 4×4 silicon photomultipliers through an optical window. The measurements were conducted using 81 keV and 356 keV gamma-rays from a collimated 133Ba source. The 3D position reconstruction of interaction points was performed using artificial neural networks trained with experimental data. Although the position resolution was significantly better for the thinner crystal, the 20 mm thick CeBr3 crystal showed an acceptable resolution of about 5.4 mm FWHM for the x and y coordinates, and 7.8 mm FWHM for the z-coordinate (crystal depth) at 356 keV. These values were obtained from the full position scans of the crystal sides. The position resolution of the LaBr3:Ce crystal was found to be considerably worse, presumably due to the highly diffusive optical in- terface between the crystal and the optical window of the enclosure. The energy resolution (FWHM) measured for 662 keV gamma-rays was 4.0% for LaBr3:Ce and 5.5% for CeBr3. The same crystals equipped with a PMT (Hamamatsu R6322-100) gave an energy resolution of 3.0% and 4.7%, respectively.

A. Ulyanov, O. Morris, O. Roberts, et. al.
Fri, 20 Jan 17
41/51

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# Ion beam test results of the Plastic Scintillator Detector of DAMPE [IMA]

The DArk Matter Particle Explorer (DAMPE) is one of the four satellites within Strategic Pioneer Research Program in Space Science of the Chinese Academy of Science (CAS). DAMPE can detect electrons, photons and ions in a wide energy range (5 GeV to 10 TeV) and ions up to iron (100GeV to 100 TeV). Plastic Scintillator Detector (PSD) is one of the four payloads in DAMPE, providing e/{\gamma} separation and charge identification up to Iron. An ion beam test was carried out for the Qualification Model of PSD in CERN with 40GeV/u Argon primary beams. The Birk’s saturation and charge resolution of PSD were investigated.

R. Qiao, W. Peng, D. Guo, et. al.
Thu, 19 Jan 17
1/42

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# DAMPE space mission: first data [HEAP]

The DAMPE (DArk Matter Particle Explorer) satellite was launched on December 17, 2015 and started its data taking operation a few days later.
DAMPE has a large geometric factor ($\sim~0.3\ m^2\ sr$) and provides good tracking, calorimetric and charge measurements for electrons, gammas rays and nuclei. This will allow precise measurement of cosmic ray spectra from tens of $GeV$ up to about $100\ TeV$. In particular, the energy region between $1-100\ TeV$ will be explored with higher precision compared to previous experiments. The various subdetectors allow an efficient identification of the electron signal over the large (mainly proton-induced) background. As a result, the all-electron spectrum will be measured with excellent resolution from few $GeV$ up to few $TeV$, thus giving the opportunity to identify possible contribution of nearby sources. A report on the mission goals and status is presented, together with the on-orbit detector performance and the first data coming from space.

F. Gargano
Thu, 19 Jan 17
17/42

Comments: XXV ECRS 2016 Proceedings – eConf C16-09-04.3

# Performance of a prototype active veto system using liquid scintillator for a dark matter search experiment [IMA]

We report the performance of an active veto system using a liquid scintillator with NaI(Tl) crystals for use in a dark matter search experiment. When a NaI(Tl) crystal is immersed in the prototype detector, the detector tags 48% of the internal K-40 background in the 0-10 keV energy region. We also determined the tagging efficiency for events at 6-20 keV as 26.5 +/- 1.7% of the total events, which corresponds to 0.76 +/- 0.04 events/keV/kg/day. According to a simulation, approximately 60% of the background events from U, Th, and K radioisotopes in photomultiplier tubes are tagged at energies of 0-10 keV. Full shielding with a 40-cm-thick liquid scintillator can increase the tagging efficiency for both the internal K-40 and external background to approximately 80%.

Wed, 18 Jan 17
8/61

Comments: Submitted to Nuclear Instruments and Methods in Physics Research Section A

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# Measurement of the muon-induced neutron seasonal modulation with LVD [HEAP]

Cosmic ray muons with the average energy of 280 GeV and neutrons produced by muons are detected with the Large Volume Detector at LNGS. We present an analysis of the seasonal variation of the neutron flux on the basis of the data obtained during 15 years. The measurement of the seasonal variation of the specific number of neutrons generated by muons allows to obtaine the variation magnitude of of the average energy of the muon flux at the depth of the LVD location. The source of the seasonal variation of the total neutron flux is a change of the intensity and the average energy of the muon flux.

N. Agafonova
Wed, 18 Jan 17
56/61

Comments: XXV ECRS 2016 Proceedings – eConf C16-09-04.3

# Prospects for measuring the neutrino mass hierarchy with KM3NeT/ORCA [CL]

ORCA (Oscillation Research with Cosmics in the Abyss) is the low-energy branch of KM3NeT, the next-generation research infrastructure hosting underwater Cherenkov detectors in the Mediterranean Sea. ORCA’s primary goal is the determination of the neutrino mass hierarchy by measuring the matter-induced modifications on the oscillation probabilities of few-GeV atmospheric neutrinos. The ORCA detector design foresees a dense configuration of KM3NeT neutrino detection technology, optimised for measuring the interactions of neutrinos in the energy range of 3 – 20 GeV. To be deployed at the French KM3NeT site, ORCA’s multi-PMT optical modules will exploit the excellent optical properties of deep-sea water to accurately reconstruct both shower-like (mostly electron neutrino) and track-like (mostly muon neutrino) events in order to collect a high-statistics sample of few-GeV neutrino events. This contribution reviews the methods and technology of the ORCA detector, and discusses the prospects for measuring the neutrino mass hierarchy as well as the potential to improve the measurement precision on other oscillation parameters.

Tue, 17 Jan 17
20/81

Comments: XXV ECRS 2016 Proceedings – eConf C16-09-04.3

# Energy spectrum of cascade showers generated by cosmic ray muons in water [HEAP]

The spatial distribution of Cherenkov radiation from cascade showers generated by muons in water has been measured with Cherenkov water calorimeter (CWC) NEVOD. This result allowed to improve the techniques of treating cascade showers with unknown axes by means of CWC response analysis. The techniques of selecting the events with high energy cascade showers and reconstructing their parameters are discussed. Preliminary results of measurements of the spectrum of cascade showers in the energy range 100 GeV – 20 TeV generated by cosmic ray muons at large zenith angles and their comparison with expectation are presented.

R. Kokoulin, N. Barbashina, A. Bogdanov, et. al.
Tue, 17 Jan 17
26/81

Comments: XXV ECRS 2016 Proceedings – eConf C16-09-04.3

# Results of measurements of the flux of albedo muons with NEVOD-DECOR experimental complex [HEAP]

Results of investigations of the near-horizontal muons in the range of zenith angles of 85-95 degrees are presented. In this range, so-called “albedo” muons (atmospheric muons scattered in the ground into the upper hemisphere) are detected. Albedo muons are one of the main sources of the background in neutrino experiments. Experimental data of two series of measurements conducted at the experimental complex NEVOD-DECOR with the duration of about 30 thousand hours “live” time are analyzed. The results of measurements of the muon flux intensity are compared with simulation results using Monte-Carlo on the basis of two multiple Coulomb scattering models: model of point-like nuclei and model taking into account finite size of nuclei.

S. Khokhlov, N. Barbashina, A. Bogdanov, et. al.
Tue, 10 Jan 17
3/75

Comments: XXV ECRS 2016 Proceedings – eConf TBA

# On the coherent emission of radio frequency radiation from high energy particle showers [IMA]

Extended Air Showers produced by cosmic rays impinging on the earth atmosphere irradiate radio frequency radiation through different mechanisms. Upon certain conditions, the emission has a coherent nature, with the consequence that the emitted power is not proportional to the energy of the primary cosmic rays, but to the energy squared. The effect was predicted in 1962 by Askaryan and it is nowadays experimentally well established and exploited for the detection of ultra high energy cosmic rays.
In this paper we discuss in details the conditions for coherence, which in literature have been too often taken for granted, and calculate them analytically, finding a formulation which comprehends both the coherent and the incoherent emissions. We apply the result to the Cherenkov effect, obtaining the same conclusions derived by Askaryan, and to the geosynchrotron radiation.

E. Conti and G. Sartori
Tue, 10 Jan 17
31/75

Comments: 9 pages, 2 figures. Submitted to International Journal of Modern Physics D. arXiv admin note: substantial text overlap with arXiv:1511.03562

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# Towards an Experimental Determination of the Transition Strength Between the Ground States of $^{20}$F and $^{20}$Ne [CL]

Electron capture on $^{20}$Ne is thought to play a crucial role in the final evolution of electron-degenerate ONe stellar cores. Recent calculations suggest that the capture process is dominated by the second-forbidden transition between the ground states of $^{20}$Ne and $^{20}$F, making an experimental determination of this transition strength highly desirable. To accomplish this task we are refurbishing an intermediate-image magnetic spectrometer capable of focusing 7 MeV electrons, and designing a scintillator detector surrounded by an active cosmic-ray veto shield, which will serve as an energy-dispersive device at the focal plane.

O. Kirsebom, J. Cederkall, D. Jenkins, et. al.
Mon, 9 Jan 17
37/52

Comments: 4 pages, 1 figure, NIC-XIV

# KM3NeT-ORCA: Oscillation Research with Cosmics in the Abyss [CL]

KM3NeT, currently under construction in the abysses of the Mediterranean Sea, is a distributed research infrastructure that will host a km3-scale neutrino telescope (ARCA) for high-energy neutrino astronomy, and a megaton scale detector (ORCA) for neutrino oscillation studies of atmospheric neutrinos. ORCA is optimised for a measurement of the mass hierarchy, providing a sensitivity of 3{\sigma} after 3-4 years. It will also measure the atmospheric mixing parameters $\Delta m_{32}^2$ and $\theta_{23}$ with a precision comparable to the NOvA and T2K experiments using both the muon neutrino disappearance and tau neutrino appearance channels. It will provide a measurement of the tau neutrino appearance rate with better than 10% precision, a crucial ingredient for tests of unitarity. It will probe the octant of the mixing angle $\theta_{23}$ via matter resonance effects on neutrinos and antineutrinos crossing the core and mantle, which are largely independent on the CP phase. The observation of neutrino oscillations over a wide range of baselines and energies will provide broad sensitivity to new physics such as non-standard neutrino interactions (NSI) and sterile neutrinos.

P. Coyle
Fri, 6 Jan 17
6/46

Comments: 27th International Conference on Neutrino Physics and Astrophysics (Neutrino 2016)

# Search for Electronic Recoil Event Rate Modulation with 4 Years of XENON100 Data [CEA]

We report on a search for electronic recoil event rate modulation signatures in the XENON100 data accumulated over a period of 4 years, from January 2010 to January 2014. A profile likelihood method, which incorporates the stability of the XENON100 detector and the known electronic recoil background model, is used to quantify the significance of periodicity in the time distribution of events. There is a weak modulation signature at a period of $431^{+16}_{-14}$ days in the low energy region of $(2.0-5.8)$ keV in the single scatter event sample, with a global significance of $1.9\,\sigma$, however no other more significant modulation is observed. The expected annual modulation of a dark matter signal is not compatible with this result. Single scatter events in the low energy region are thus used to exclude the DAMA/LIBRA annual modulation as being due to dark matter electron interactions via axial vector coupling at $5.7\,\sigma$.

XENON. collaboration, E. Aprile, J. Aalbers, et. al.
Wed, 4 Jan 17
5/39

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# Precision measurement of antiproton to proton ratio with the Alpha Magnetic Spectrometer on the International Space Station [HEAP]

A precision measurement by AMS of the antiproton-to-proton flux ratio in primary cosmic rays in the absolute rigidity range from 1 to 450 GV is presented based on $3.49\times10^5$ antiproton events and $2.42\times10^9$ proton events. Above $\sim60$ GV the antiproton to proton flux ratio is consistent with being rigidity independent. A decreasing behaviour is expected for this ratio considering the traditional models for the secondary antiproton flux.

F. Nozzoli
Tue, 3 Jan 17
7/55

Comments: XXV ECRS 2016 Proceedings – eConf C16-09-04.3

# Effect of pressure and temperature corrections on muon flux variability at ground level and underground [CL]

In Low Background Laboratory at Institute of Physics Belgrade, plastic scintillators are used to continuously monitor flux of the muon component of secondary cosmic rays. Measurements are performed on the surface as well as underground (25 m.w.e depth). Temperature effect on muon component of secondary cosmic rays is well known and several methods to correct for it are already developed and widely used. Here, we apply integral method to calculate correction coefficients and use GFS (Global Forecast System) model to obtain atmospheric temperature profiles. Atmospheric corrections reduce variance of muon flux and lead to improved sensitivity to transient cosmic ray variations. Influence of corrections on correlation with neutron monitor data is discussed.

M. Savic, A. Dragic, N. Veselinovic, et. al.
Tue, 3 Jan 17
14/55

Comments: XXV ECRS 2016 Proceedings – eConf C16-09-04.3

# Low Threshold Results and Limits from the DRIFT Directional Dark Matter Detector [IMA]

We present results from a 54.7 live-day shielded run of the DRIFT-IId detector, the world’s most sensitive, directional, dark matter detector. Several improvements were made relative to our previous work including a lower threshold for detection, a more robust analysis and a tenfold improvement in our gamma rejection factor. After analysis, no events remain in our fiducial region leading to an exclusion curve for spin-dependent WIMP-proton interactions which reaches 0.28 pb at 100 GeV/c^2 a fourfold improvement on our previous work. We also present results from a 45.4 live-day unshielded run of the DRIFT-IId detector during which 14 nuclear recoil-like events were observed. We demonstrate that the observed nuclear recoil rate of 0.31+/-0.08 events per day is consistent with detection of ambient, fast neutrons emanating from the walls of the Boulby Underground Science Facility.

J. Battat, A. Ezeribe, J. Gauvreau, et. al.
Tue, 3 Jan 17
29/55